Offhand Grinding. Chapter 11

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Chapter 11 Offhand Grinding LEARNING OBJECTIVES After studying this chapter, students will be able to: Identify the various types of offhand grinders. Dress and true a grinding wheel.

1 Chapter 11 Offhand Grinding LEARNING OBJECTIVES After studying this chapter, students will be able to: Identify the various types of offhand grinders. Dress and true a grinding wheel. Prepare a grinder for safe operation. Use an offhand grinder safely. List safety rules for offhand grinding. INSTRUCTIONAL MATERIALS Text: pages Test Your Knowledge Questions, pages Workbook: pages Instructor s Resource: pages Guide for Lesson Planning Research and Development Ideas Reproducible Masters: 11-1 Grinding Machine Operation 11-2 Adjusting Grinder Tool Rest 11-3 Using Wheel Dressers 11-4 Test Your Knowledge Questions Color Transparency (Binder/CD only) GUIDE FOR LESSON PLANNING Have students read and study Chapter 11, paying attention to the illustrations. Reproducible Masters can be used on the overhead projector or copied and distributed to the class. Review the assignment and discuss or demonstrate the following: Definition of grinding. Use Reproducible Master When offhand grinding is usually used. Types of offhand grinders. Checking grinding wheels for safe operation. Importance of properly adjusted tool rest. Use Reproducible Master How to dress a grinding wheel. Use Reproducible Master When to use a dry-type grinder. When a wet-type grinder is used. Safety procedures to be observed when using offhand grinding machines. When demonstrating offhand grinding techniques, be sure that: Equipment is properly adjusted with all guards and safety devices in place. Students/trainees are wearing approved eye protection. Grinding wheels are solid, dressed, and running true. Students understand what metals can or cannot be ground on shop/lab grinding machines. Briefly review the demonstrations and encourage students to ask questions. 153

2 154 Technical Terms Review the terms introduced in the chapter. New terms can be assigned as homework, extra credit, or used for a quiz. The following list is also given at the beginning of the chapter. abrasive belt precision microgrinder grinding machines reciprocating bench grinder hand grinder concentricity temper flexible shaft grinders tool rest pedestal grinder wheel dresser Review Questions Assign Test Your Knowledge questions. Copy and distribute Reproducible Master 11-4 or have students use the questions on pages and write their answers on a separate sheet of paper. Workbook Assignment Assign Chapter 11 of the Machining Fundamentals Workbook. Research and Development Discuss the following topics in class or have students complete projects on their own. 1. How are natural sandstone grinding wheels made? Secure samples of natural sandstone and compare them with manufactured abrasives. What, in your opinion, makes the manufactured abrasive superior to the natural product? 2. Research the term MOH SCALE. Prepare a chart showing the common abrasives in order of their hardness. Secure samples to mount on the chart. 3. Grinders used by 18th century workers required them to work in an unusual position. Prepare a brief presentation for the class on how they worked, some of the health problems they had because of their job, and some of the articles they produced. Create visual aids (photos, drawings, transparencies), for use during the presentation. 4. Borrow an old fashioned natural sandstone grinding machine. Demonstrate its use to the class. 5. True and dress the grinding wheels used on the machines in the shop. 6. Secure a list of the various grades and types of grinding wheels available from a typical abrasive manufacturer. Machining Fundamentals Instructor s Resource TEST YOUR KNOWLEDGE ANSWERS, Pages Grinding is an operation that removes material by rotating an abrasive wheel or belt against work. 2. Evaluate individually. 3. offhand 4. c. Work is manipulated with fingers until desired shape is obtained. 5. Dry type and wet type. The dry type does not use a flow of coolant on wheel. The wet type uses a flow of coolant over wheel. 6. 1/16, 1.5, pulled, rest, wheel 7. Supporting it on a section of wire and lightly tapping it with a light metal bar or screwdriver handle. A good wheel will give off a clear ringing sound. 8. c. Stand to one side of the grinder when using the machine. 9. burn 10. wet 11. crowned; It will minimize the amount of contact between the wheel and the work. This reduces the risk of the work being damaged or destroyed by excessive heat. 12. checking it for soundness 13. Evaluate individually. Refer to Section WORKBOOK ANSWERS, Pages belt, disc 2. d. All of the above. 3. roughing, finish grinding 4. c. keeps the wheels constantly flooded with fluid 5. d. All of the above. 6. Serious injury could result if the cloth is pulled into the wheel. 7. d. All of the above. 8. wheel dresser 9. c. use the face of the wheel, not the sides 10. grooves/ridges 11. a. Diamond-impregnated 12. c. being damaged or destroyed by excessive heat buildup 13. greater 14. d. All of the above. 15. Evaluate individually. Refer to Section 11.4.

3 Chapter 11 Offhand Grinding 155 Grinding Machine Operation Work Work Grinding Wheel Abrasive Belt Driver pulley Work Worktable Abrasive Belt Machining Copyright Goodheart-Willcox Co., Inc. 11-1

4 156 Machining Fundamentals Instructor s Resource Adjusting Grinder Tool Rest 1/16 (1.5 mm) Maximum clearance Copyright Goodheart-Willcox Co., Inc. 11-2

Chapter 11 Offhand Grinding 157 Using Wheel Dressers Tool rest Heel of wheel dresser hooks over tool rest Move the tool back and forth over the face of the stone.

5 Chapter 11 Offhand Grinding 157 Using Wheel Dressers Tool rest Heel of wheel dresser hooks over tool rest Move the tool back and forth over the face of the stone. Diamond tip Guide block Tool rest Diamond tip-type wheel dresser Industrial diamonds are also used to dress and true grinding wheels. The guide block is used for grinders with slotted tool rests. Copyright Goodheart-Willcox Co., Inc. 11-3

6 158 Machining Fundamentals Instructor s Resource Offhand Grinding Name: Date: Score: 1. Describe the grinding operation. 2. How do abrasive belt grinders differ from abrasive wheel grinders? 3. Bench and pedestal grinders are used to do grinding. 4. The grinding technique referred to in the preceding 4. statement is so named because: a. It can only do external work. b. Work is too hard to be machined by other methods. c. Work is manipulated with fingers until desired shape is obtained. d. All of the above. e. None of the above. 5. Name the two types of pedestal grinders. How do they differ? 6. The tool rest should be about inches or mm away from the grinding wheel or belt for safety. This prevents the possibility of work being between the tool and Copyright Goodheart-Willcox Co., Inc (continued)

7 Chapter 11 Offhand Grinding 159 Name: 7. How can grinding wheel soundness be checked? 8. Since a grinding wheel cannot be checked each time the 8. grinder is used, it is recommended that the operator: a. Not use the grinder. b. Check with the instructor whether the wheel is sound. c. Stand to one side of the grinder when using the machine. d. All of the above. e. None of the above. 9. Work will if it is forced against the wheel with too much pressure. 10. Carbide-tipped tools are usually sharpened on a grinder. 11. The face of wheel on a wet-type grinder is slightly. Why is this done? 12. Never mount a grinding wheel on a grinder without. 13. List four safety precautions to be observed when operating a grinder Copyright Goodheart-Willcox Co., Inc. 11-4

8 160 Machining Fundamentals Instructor s Resource

Other Lathe Operations

Chapter 15 Other Lathe Operations LEARNING OBJECTIVES After studying this chapter, students will be able to: Safely set up and operate a lathe using various work-holding devices. Properly set up steady